Vanadium-columbium-tantalum alloys



United States Patent 01 iice Patented June 10, 1969 3,449,118VANADIUM-COLUMBIUM-TANTALUM ALLOYS Frederick C. Holtz, Jr., Evanston,Ill., assignor, by mesne assignments, to the United States of America asrepresented by the Secretary of the Navy Filed Nov. 15, 1966, Ser. No.594,583 Int. Cl. C22c 1/02, 27/00; C21d 1/78 US. Cl. 75--134 10 ClaimsABSTRACT OF THE DISCLOSURE A vanadium-columbium-tantalum alloy withaddition of titanium, silicon and carbon, characterized by high tensilestrength and ductility at a range of temperatures from 320 F. to 2000 F.

This invention relates to a vanadium base alloy containing columbium andtantalum with small additives of silicon and carbon.

Previous vanadium alloy studies had indicated that vanadium-columbiumbase compositions had attractive short-time strength properties in the1800" to 240 F. range. Limited testing at temperatures as low as 452 F.(259 C.) showed these materials to be unusually strong and ductile. Thepresent work was aimed at producing dispersion-strengthened compositionswhich would not only have good cryogenic properties but also goodretention of strength at temperatures above that at which the nickel andcobalt base superalloys are used. Because of their comparatively lowmelting point, these alloys were not expected to be as strong ascolumbium, molybdenum, or other refractory alloys at temperatures inexcess of 2400 F. However, the excellent fabrication characteristics andthe ability to form reliable silicide oxidation-protective coatingsindicate high potential for use over a wide range of temperatures. Thedevelopment of space craft finds a need for alloys which will retaintheir strength at both low and high temperatures.

The object of the present invention is to provide an alloy or group ofalloys which excel in fabricability, ductility and high strength over arange from -320 F. to at least 2400 F.

Another object of the present invention is to provide a group of alloyswhich will have high strength at extremes of low and high temperaturesand which will form oxidation-protective coating.

Still another object of the present invention is to provide a vanadiumbased alloy containing columbium and tantalum and additives of siliconand carbon.

Other objects will be apparent from the subsequent disclosure andappended claims.

The drawing is a graph showing ultimate tensile strength data comparingtwo vanadium-columbium-tantalum base alloys with other alloys.

The alloys which are the subject of this invention are based on aV-C-b-Ta system with small additives of Si and C.

Materials used:

In the experimental procedures a single lot of vanadium melting stockwas used with the following analysis of the V.

Oxygen 0.040 Nitrogen 0.02.8 Carbon 0.040 Hydrogen 0.004 Iron 0.050Silicon 0.020

Nonconsumable-electrode arc-melted ingots of this melting stock hadhardness levels in the VPN (10 kg.) 160- 170 range.

Columbium sheet used as melting stock was electronbeam melted and hadless than 0.01 wt. percent total oxygen and nitrogen. Tantalum sheet ofsimilar purity was used. Minor additions such as Zirconium, silicon weremade from high-purity commercial melting stock. Carbon was added as anarc-melted V-5 C master alloy.

Percentages of materials used:

Percent Columbium 25-40 Tantalum 20 30 Titanium 1 Silicon 0.15 015Carbon 0.0370.l25 Vanadium, remainder to make INGOT PREPARATION (l)Melting All of the compositions were prepared by nonconsumable-electrodearc-melting under a highly purified argon atmosphere. Ingot weightsranged from to 200 grams, depending on density, and the ingots wereinverted and remelted five times to insure good homogeneity. Theseingots were approximately 0.4 in. thick by 2.5 in. in diameter.

(2) Thermal homogenization The arc-melted ingots were thermallyhomogenized in a tantalum-element resistance-heated furnace. These heattreatments were conducted under vacuum (10 torr or better) or in argonwhich was purified by passing the gas through hot titanium sponge and aliquid nitrogen trap. After heating for the desired length of time, theingots were lowered from the hot zone and cooled by a stream of flowingargon at a rate of approximately 400 F./min.

(3) Ingot fabrication The initial ingot breakdown for nearly all of thealloys was achieved by hammer forging. The ingots were jacketed in 0.030in. thick stainless steel, then evacuated. Hammer forging was done at23502400 F. on a mechanical drop hammer. Reductions in thickness of 30to 40% were used to obtain a final forged thickness of 0.25 to 0.30 in.The more diflicult-to-work alloys required reheating to achieve thisreduction. After forging, jackets were stripped and any edge or surfacecracks were removed by grinding. The conditioned ingots were thencold-rolled, in most cases with intermediate vacuum annealing, to sheetranging in thickness from 0.004 to 0.027 in. Rolling reduction wasinitially 10% per pass, although smaller reductions were used when thesheet was less than 0.030 in. thick. A list of representativecompositions together with the procuring methods and results of ingotfabrication is presented in Table I.

TABLE I.VANADIUM ALLOY FABRICATION DATA Density, Composition, wt.percent 1 lb./in. Fabrication Procedures ResultsV400h30Ta-1Ti-0.5Si-0.075C 3i HF gigg igg- 02 mV-40Cb30Ta-1Ti-0.25Si-0.037C 0.31 HF-CR.- Slight cracking at 0.35 in.V-40Cb-30'1a-1Ti-0.25Si-0.025C. 0. 31 HF-G R-Ann- Some Surface cracks in0.004 in. foil.

o. 31 HF-C R-Ann-CR:

V-35G b-30Ta-1Ti-0.25Si-0.05C

HF-C R-Ann-C R Good sheet, 0028 in.

nn-CR. Some cracking in 0.025 in. sheet.

Moderate cracking at 0.035 in.

Slight surface cracking in 0.008 in. sheet. Slight surface cracking in0.008 in.

Very slight edge cracking at 0.04 in.

Cracked at 0.17 in.

Cracked severely.

I1 TH=thermal homogenization: 3 hr. at 2,800 F., 4 hr. at 2,300 and2,600" F.; HF=hammer forge; Ann=vacuurn anneal 4 In".

at 2,000 to 2,400 F.; CR=cold r011.

RECRYSTALLIZATION cooled from the annealing temperature at a rate ofabout 250 F./min. to room tempertaure, then cold-rolled to reductions inthickness of 6080%. Aging was conducted at temperatures from 1200 to1600 F. Most of the aged specimens were evaluated by room temperaturetensile tests.

CRYOGENIC TENSILE PROPERTIES The alloys were tested for tensile strengthat temperatures as low as that of liquid nitrogen (320 F.). The testedspecimens had a A by 1 in. gage section, and were tested at a strain of0.005 in./in./min. The results are shown in Table III.

TABLE III.-TENSILE DAT IA FOR VANADIUM ALLOYS AT LIQUID NITROGENEMPERATURE (320 F.)

Density- Ultimate Corrected Tensile Total Strength,

Strength, Elongation, U.I.S./

Composition, wt. percent Treatment p.s.i. percent (lb./in.

V-Cb-30Ta-1Tl-0.25Si-0.035C Aged 1,300 F., 5 hr 370, 000 7. 7 1,200,000V-25Cb-20Ta-1Ti0.l5Si-0.075C Aged 1,300 F., 5 hr 350, 000 14. 2 1, 282,000

B Aging treatments after -80% reduction by cold rolling.

TABLE IV.-ROOM-TEMPERATURE TENSILE DATA FOR FULLY ANNEALED VANADIUMALLOYS 2,200 F., 30 min.

TABLE IL-RECRYSTALLIZATION AND HARDNESS DATA FOR VANADIUM ALLOYSRecrystallization Hardness, Composition, wt. Percent Temp., F. VPN

V-40Cb-30TaF1Ti-0.25Si-0.025G 1, 900 426 V-35Cb-30Ta-1Ti-0.25Si-0.035C2, 000 426 V-35Gb-25Ta-1Ti-0.2Si-0.03C 1, 900 390V-30Cb-20Ta-1Ti-0.25Si-0.05C 1, 907 308 V-25Cb-20Ta-1Ti-0.15Si'0.075C 1,900 358 V-25Cb-20Ta-1Ti-0.25Si-0.125C 2, 000 348 AGING RESPONSE Studiesof aging behavior were carried out on selected alloys of the V-Cb-Tasystem. Sheet specimens were fully ROOM TEMPERATURE TENSILE PROPERTIESTensile results for the V-Cb-Ta base alloys show generally decreasingstrength with increasing vanadium content. One of the alloys shown inTable IV had an elongation of 21%, a value comparable to those of highvanadium alloys.

ELEVATED-TEMPERATURE TENSILE PROPERTIES Tests for tensile strength wereconducted on sheet specimens of alloys at 1200, 1800, 2000, 2200 and2400 F. using a strain rate of 0.05 in./in./min. The sheet stock wasapproximately 0.008 in. thick and the specimens were tested in theas-rolled, fully annealed and cold-rolled and annealed for 30 min. at2000 F. The specimens were aged condition.

TABLE V.ELEVATED-TEMPE RATURE TENSILE DATA FOR V-Cb-Ta BASE ALLOYSDensity- Ultrmate Corrected Test Tensile Elon- Strength, Temp.,Strength, gatlon, U.T.S./ Composition, wt. percent Treatment F p.s.i.percent (lbJinfl) V-40Cb-30'Ia-1'Ii-0.25Si-0.025C Annealed 2,400 F., 30min- 2,000 86, 700 8 276,000 v-35Cb 30Ta 1Ti 0,25si0.035C Annealed 2,200F., 30 min." 1, 200 164, 000 12 534, 000 Cold rolled; aged 1,200 F., 48hr. 1, 200 232,000 3 736, 000 Cold rolled 60% 1, 800 134, 000 15 437,000 Annealed 2,200 F. 1, 800 120,000 7. 6 392, 000 Cold rolled 60% 2,400 22, 100 68 72, 000 V-35Cb-25Ia-1Ti-0.2Si-0.03C Annealed 2,400 F., 301I1in-"-. 2,000 73,200 b 248, 000 V-30Cb-201a-1Ti-0.25Si-0.05C Annealed2,400 F., 30 min. 1 2, 000 70,000 b 251, 000V-25Cb-20Tar1Ti-0.15Si-0.075C A Cold rolled; aged 1,300 F-, 4 h! 1, 200182,000 1. 5 668, 000 Cold rolled; aged 1,300 F., 4 hr 1,800 84, 000 20307, 000 Annealed 2,200 F., 30 min 1, 800 104, 000 14 382, 000 Coldrolled; aged 1,300 F., 4 h 2, 200 31, 700 40 116, 000 Annealed 2,200 F.,30 min. 2, 200 44, 000 19 161, 000

' Cooled at 250 F./min.

Referring to the drawings, it will be seen that twovanadium-columbium-tantalum base alloys compare favorably with thecryogenic alloys (stainless steel and titanium base) at low temperaturesand do not exhibit the sharp decrease in strength. They are stronger ona density corrected basis than the nickel-base superalloy at alltemperatures.

Density-corrected strength data for the high-vanadium alloys would showvalues similar to those reported for the V-25 CB-ZO Ta base alloy attemperatures up to about 1200" F. At higher temperatures, the V-20 Cb-Ti base alloys lose strength more rapidly than the tantalum containingmaterials. At 2000 F., the high vanadium alloys have density correctedstrengths in the 120,000 to 179,000-in. range; similar strengths areretained by the V-25 Cb Ta base material at 2200 P.

On the basis of these strength data, the higher tantalum alloy appearsto be the best for use over a wide range of temperature.

COMPARATIVE DATA A comparison of the tensile strength of theexperimental alloys with those of commercial cryogenic and refractorymaterials shows the temperature ranges over which the vanadium alloysdemonstrate attractive properties. Vanadium alloys compare favorablywith the cryogenic alloys (stainless steel and titanium base alloys) andthe vanadium alloys do not exhibit the sharp decrease in strength above1200" F.

The vanadium alloys, enriched with silicon and carbon, exhibit excellentfabricability. They are as good as stainless steel at low temperaturesand surpass the nickelbase alloys at all test temperatures.

What is claimed is:

1. An alloy having high tensile strength and ductility at temperaturesbetween 320 F. and 2200 F. consisting essentially of -40% Cb, 2030% Ta,1% Ti, O.150.5% Si, .037-

.125 C-remainder V.

b Broke outside of gage marks:

2. An alloy according to claim 1 in which the specific proportions are40 Cb-30 Ta-l Ti-0.5 Si-0.075 C-remainder V.

3. An alloy according to claim 1 in which the specific groportions are40 Cb-30 Ta-l Ti-0.25 Si-0.075 C-remain- 4. An alloy according to claim1 in which the specific proportions are 40 Cb-30 Ta-l Ti-0.25 Si-0.037C-remainder V.

5. An alloy according to claim 1 in which the specific proportions are40 Cb-30 Ta-l Ti-0.25 Si-0.025 C-remainder V.

6. An alloy according to claim 1 in which the specific proportions are35 Cb-25 Ta-1 Ti-0.2 Si-0.03 C-remainder V.

7. An alloy according to claim 1 in which the specific proportions are30 Cb-20 Ta-l Ti-O.25 Si-0.05 C-remainder V.

8. An alloy according to claim 1 in which the specific proportions are35 Cb-30 Ta-l Ti-0.25 Si-0.035 C-remainder V.

9. An alloy according to claim 1 in which the specific proportions are25 Cb-ZO Ta-l Ti-0.15 Si-0.075 C-remainder V.

10. An alloy according to claim 1 in which the specific proportions are25 Cb-20 Ta-l Ti-O.25 Si-0.l25 C-remainder V.

References Cited UNITED STATES PATENTS 3,028,236 4/1962 Wlodek ct al.l74 3,128,178 4/1964 Duffek 75174 3,173,784 3/1965 Wlodek et al. 75134RICHARD O. DEAN, Primary Examiner.

U.S. Cl. X.R. 75174

